61 チャ植物におけるプリンヌクレオチド代謝とカフェイン生合成(ポスター発表の部)

概要

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In tea (Camellia sinensis) plants, caffeine is synthesized from xanthosine, 7-methylxanthosine, 7-methylxanthine and theobromine, and S-adenosylmethionine is utilized as the actual source of the methyl groups. In addition to the pathway leading to the formation of xanthosine, which is the first methylated purine compound for caffeine biosynthesis from AMP, IMP and XMP, the formation from guanine nucleotides is proposed, based on available evidence for the catabolism of guanine nucleotides in plants, as: GMP→guanosine→xanthosine. There are seasonal variations in the caffeine content and biosynthetic capacity for caffeine synthesis in tea leaves. The results indicated that the biosynthesis of caffeine occurs in young leaves during the early stages of shoot development (April to June) and that one of the most important limiting factors for the synthesis of caffeine is the activity of various N-methyltransferases. The metabolism of [8-^<14>C]adenine in isolated stamens and petals from the flower buds of four different species of Camellia revealed that the biosynthetic pathway to caffeine is operative in the stamens and petals of tea flowers, but the reaction from theobromine to caffeine is defficient in C. irrawadiensis, while the entire biosynthetic pathway for purine alkaloids is not functional in flowers of C. japonica and C. sasanqua, as it is in leaves of these Camellia plants.
天然有機化合物討論会の論文
1991-09-07